199970021 has 2 divisors, whose sum is σ = 199970022. Its totient is φ = 199970020.

The previous prime is 199970011. The next prime is 199970047. The reversal of 199970021 is 120079991.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 185232100 + 14737921 = 13610^2 + 3839^2 .

It is an emirp because it is prime and its reverse (120079991) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-199970021 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (199970011) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 99985010 + 99985011.

It is an arithmetic number, because the mean of its divisors is an integer number (99985011).

Almost surely, 2^199970021 is an apocalyptic number.

It is an amenable number.

199970021 is a deficient number, since it is larger than the sum of its proper divisors (1).

199970021 is an equidigital number, since it uses as much as digits as its factorization.

199970021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 10206, while the sum is 38.

The square root of 199970021 is about 14141.0756662992. The cubic root of 199970021 is about 584.7743264732.

The spelling of 199970021 in words is "one hundred ninety-nine million, nine hundred seventy thousand, twenty-one".